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σ γ / k 0 measurements at Budapest PGAA facility

σ γ / k 0 measurements at Budapest PGAA facility. Zsolt R évay , László Szentmiklósi Institute of Isotopes Budapest. Practice of PGAA in Budapest. k 0 method Relative standardization Inelastic neutron scattering ( n,n’ γ ) background Using Hypermet

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σ γ / k 0 measurements at Budapest PGAA facility

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  1. σγ / k0 measurements at Budapest PGAA facility Zsolt Révay, László Szentmiklósi Institute of Isotopes Budapest

  2. Practice of PGAA in Budapest • k0 method • Relative standardization • Inelastic neutron scattering (n,n’γ) background • Using Hypermet • Handling asymmetric peaks and overlaps • Non-linearity • Efficiency

  3. Whyk0method? • Most accurate source of needed data • k0 philosophy guarantees the highest reliability in measurements • k0 idea can be better approximated in a beam • Should be improved

  4. Advantages of measurements in (cold) neutron beam • No epithermal neutrons • No non-1/v behavior (in cold beam) • Lambert-Beer type self-shielding (low-divergence beam instead of isotropic neutron field)

  5. Research Reactor • 20 MW • water cooled • water moderated • thermal flux 1014 cm-2 s-1

  6. Neutron guides • Ni or supermirror guides • relatively small losses • low background

  7. Cold neutron source at Budapest 400 cm320 K liquid H2

  8. Budapest PGAA facility • 10 MW • LH cold source • curved guide • Compton-suppressed HPGe • chopper

  9. Budapest PGAA and NIPS facilities

  10. PGAA facility

  11. Compton suppression

  12. 1992 upgraded reactor starts1995 first PGAA measurement on the thermal beam1997–1998 establishment of PGAA data library1999–2000 applications2001 new cold beam2002 –2004 Handbook and Atlas

  13. Main results in methodology • Data library transportable to other labs • evaluation software • complete analysis • analytical precision for the important elements relative uncertainty: 1–2% • application of chopped beam

  14. Hypermet-PC

  15. Hypermet-PC • Asymmetric peak shape • Non-linearity • Efficiency fit • Partial peak shape calibration

  16. Efficiency • One absolute source • Lines from relative sources are normalized to it • 200-300 data points • 0.2% uncertainty at mid energy range • 2% uncertainty at high energy range

  17. Semiempirical efficiency function

  18. Measured efficiency

  19. Incorrect linear interpolation of the efficiency

  20. The “elbow” of the efficiency

  21. Prompt k0 project

  22. Measurements of elements

  23. Standardization

  24. PGAA library

  25. Verification

  26. Prompt k0 factors • relative to Cl 1951 keV line • relative to H 2223 keV line • σγ = θ γ σ

  27. Decay gammas in PGAA spectra • can be used for analysis, too • k0-s can be measured • depending on half-life, saturation correction needed

  28. Prompt saturation factor • activation and decay at the same time

  29. Activation

  30. Advantages of the in-beam measurement compared tocyclic activation • uncertainties from • half-life • timing do not accumulate

  31. k0-s for short lived nuclides

  32. Chopped-beam PGAA TOF

  33. Beam chopper • Beam periodically shielded by Gd, 6Li • Variable opening: 0.2 – 50% • variable frequency: 3 – 100 Hz

  34. Time of flight chopper detector gamma radiation n Rotating and standing slits

  35. Cold and thermal neutron spectra

  36. Candidates for in-beam measurement < 1 s: Na, < 1 min: F, Sc, Ge, Pd, Ag, In, Er, Hf, W, < 10 min Mg, Al, V, Cr, Se, Br, Rh, Dy, Ir, < 1 h: Ga, Rb, Sn, I, Pr, Nd, Ta, Re, <1 day: Mn, Cu, Sr, Cs, Ba, Eu, Lu, longer: As, Ru, La, Ce, Tb, Ho, Yb, Au,

  37. Isotopes with high Er Q0 Er Isot sigma 1.12 2280 37S 0.15 1.14 1040 64Cu 2.17 1.908 2560 65Zn 0.76 2.38 3540 75mGe 0.17 1.57 3540 75Ge 0.34 5.93 4300 90mY 0.001 5.05 6260 95Zr 0.0499 1.8 2950 131I 6.2 1.2 1540 143Ce 0.95

  38. First prototype of chopper

  39. Budapest PGAA facility (L. Sz.)

  40. Beam open prompt gamma rays decay gamma rays Usual PGAA spectrum Beam closed only decay gamma rays cyclic NAA spectrum Simultaneous PGAA and NAA measurement with a chopper

  41. Prompt and decay spectrum of Tc-99

  42. Background

  43. Mea-sure-ments

  44. Spectra

  45. Prompt and decay spectrum of Ag

  46. Results

  47. Second prototype chopper

  48. In-beam saturation factor (B) (LSz) Type I nuclides, on-line counting Type IV nuclides Type IV/B nuclides Count rate of #3 from Bateman-Rubinson equations: Type IV/A nuclides

  49. Results 1/3 (LSz) • Literature data taken from: • F. De Corte, A. Simonits, Atomic Data and Nuclear Data Tables 85 (2003) 47. • S. Roth, F. Grass, F. De Corte, L. Moens, K. Buchtela, J. Radioanal. Nucl. Chem. 169 (1993) 159. • S. Van Lierde, F. De Corte, D. Bossus, R. Van Sluijs, S. Pommé, Nucl. Instr. Meth. A 422 (1999) 874.

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